Assembly programming. The SPI Shield which you will be assembling soon has two g

ID: 3787714 • Letter: A

Question

Assembly programming. The SPI Shield which you will be assembling soon has two green status LEDs. They are connected to the two least significant bits of PORTB, as shown in schematic. The design challenge is to create software “wires” between switches 7 and 6, connected to PIND7 and PIND6, and these two green LEDs.

Currently I have the whole code working and I have the program wiring the switches to the 7-segment display and the discrete LEDs. I am very new to assembly so I am not too sure how to wire these to the two green LEDs.

Here is the last bit of my code that I have been modfying for this lab:

reset:
ldi r16, high (RAMEND) // IO[0x3e] = 0x08
out SPH, r16
ldi r16, low(RAMEND) // IO[0x3d] = 0xff
out SPL, r16
call InitShield
loop:
call ReadSwitches // read switches into r6
mov r7, r6 // wire switches to the 7 segment display
mov r8, r7 // wire switches to the 8 discrete LEDs
call WriteDisplay // write r7 to the 7 segment display and r8 to 8 discrete LEDs
rjmp loop

So I am assuming I need to modify this in order to get it to work correctly.

Schematic for given problem:

Full code if needed:

.INCLUDE <m328pdef.inc>
.CSEG
.ORG 0x0000
RST_VECT:
rjmp Reset // jump over the IVT, tables and include file(s)
.ORG 0x0100 // bypass IVT

; SPI interface registers
.DEF spiLEDS=r8
.DEF spi7SEG=r7

; Switches
.DEF switch=r6

; Temporary storage of AVR Status REGister Flag bits
.DEF reg_F=r15

; 7-segment display
.EQU seg_a=0
.EQU seg_b=1
.EQU seg_c=2
.EQU seg_d=3
.EQU seq_e=4
.EQU seg_f=5
.EQU seg_g=6
.EQU seg_dp=7

InitShield:
; Disable interrupts and configure stack pointer for 328P
cli

; Initialize Switches with Pull-up resistors and Test LEDs
   in       r16,DDRC       // input Port C Data Direction Register (0x07) for switches 5 to 0
   cbr       r16,0b00111111   // define bits 5 to 0 as input (clear bit register)
   out       DDRC,r16       // output

   in       r16,PORTC       // input Port C Register (0x08) for switches 5 to 0
   sbr       r16,0b00111111   // add pull-up resistors (PUR)
   out       PORTC,r16       // output

   in       r16,DDRD       // input Port D Data Direction Register (0x0A) for switches 7 to 6
   cbr       r16,0b11000000   // define bits 7 to 6 as input (clear)
   out       DDRD,r16       // output

   in       r16,PORTD       // input Port D Register (0x0B) for switches 7 to 6
   sbr       r16,0b11000000   // add pull-up resistors (PUR)
   out       PORTD,r16       // output

; Initialize SPI Port
   in       r16,DDRB       // Input from Port B Data Direction Register (DDRB) at i/o address 0x04
   sbr    r16,0b00101111   // Set PB5, PB3, PB2 (SCK, MOSI, SS) and PB1, PB0 (TEST LEDs) as outputs
   out    DDRB,r16       // Output to Port B Data Direction Register (DDRB) at i/o address 0x04

ldi r16,0b01010001 // Set SPCR Enable (SPE) bit 6, Master (MSTR) bit 4, clock rate fck/16 (SPR1 = 0,SPR0 = 1)
out SPCR,r16 // Output to SPI Control Register (SPCR) at i/o address 0x2c

   cbi       PORTB,2           // Clear I/O Port B bit 2 (SS) at i/o address 0x05
   cbi       PORTB,1           // Clear I/O Port B bit 1 (TEST LED1)
   cbi       PORTB,0           // Clear I/O Port B bit 0 (TEST LED0)
   ret

ReadSwitches:
; SPI Software Wires
push r17
push r16

in r17, PINC // input port C pins (0x06) into register r17
in r16, PIND // input port D pins (0x09) into register r16

cbr r17, 0b11000000 // clear non-switch bits 7 and 6
cbr r16, 0b00111111 // clear non-switch bits 5 to 0

or r16, r17 // concatenate switches SW7 - SW6 : SW5 - SW0
mov r6, r16 // move to standardized switch register

pop r16
pop r17
ret

WriteDisplay:
; Save SREG
push reg_F
in reg_F, SREG
; Start transmission of data
   out    SPDR,spiLEDS
   rcall   spiTxWait
   out       SPDR,spi7SEG
   rcall   spiTxWait
   sbi       PORTB,PB2       // strobe latches
   cbi       PORTB,PB2
; Restore SREG
   out SREG, reg_F
   pop reg_F
   ret

SpiTxWait:
   push   r16
; Wait for transmission complete
spiPolling:
   in       r16,SPSR
   bst       r16,SPIF
   brtc    spiPolling
   pop       r16
   ret

; --------------------------
reset:
ldi r16, high (RAMEND) // IO[0x3e] = 0x08
out SPH, r16
ldi r16, low(RAMEND) // IO[0x3d] = 0xff
out SPL, r16
call InitShield
loop:
call ReadSwitches // read switches into r6
mov r7, r6 // wire switches to the 7 segment display
mov r8, r7 // wire switches to the 8 discrete LEDs
call WriteDisplay // write r7 to the 7 segment display and r8 to 8 discrete LEDs
rjmp loop

Register 6 Digital Pin 7 PD7 7 Digital Pin 6 PD66 L Analog Pin 5 PC5 5 Analog Pin 4 PCA 4 Analog Pin 3 PC3 3 Analog Pin 2 PC2 2 Analog Pin 1 PC1 1 SW. Analog Pin 0 PCO 0 PORTBO DigitalPin 8 w PORTB1 Digital in 9 A DigitalPin 4 PD4 PORTD3 DigitalPin 3

Explanation / Answer